1. Field of the Invention
The present invention relates to a speaker damper having a conductive member to input an audio signal to a voice coil and also relates to method and apparatus for manufacturing such a damper.
2. Description of the Related Art
Hitherto, to simplify a wiring structure to the voice coil, as shown in FIG. 1, there has been known a speaker damper comprising a damper main body 1 and two conductive members 2. The damper main body is constructed in a manner such that a thermosetting resin such as a phenol resin or the like is impregnated into a damper raw material comprising a cloth material such as woven cloth, unwoven cloth, or the like and a wove-shaped corrugation is integrally formed by a thermal molding work. The conductive materials are attached from the inner peripheral portion to the outer peripheral portion along the shape of the corrugation. The conductive members are used as current supplying means to a coil which is provided at the center of the damper.
As methods and apparatuses for manufacturing such a speaker damper, the following methods have been known.
(1) As shown in FIG. 2, after the conductive member was adhered onto the damper raw material comprising the cloth material such as woven cloth, unwoven cloth, or the like by using an adhesive agent, they are allowed to pass in a treating bath in which a thermosetting resin such as a phenol resin or the like which was diluted by a solvent is enclosed, thereby impregnating the thermosetting resin into the damper raw material. Then, the solvent is evaporated and the resin tackiness is eliminated. In this state, the damper is thermally molded with a molding die.
(2) The thermosetting resin which was diluted by a solvent is impregnated into the damper raw material comprising the cloth material. The solvent is evaporated and the resin tackiness is eliminated. In this state, the conductive members are adhered and, thereafter, the damper is thermally molded.
(3) The thermosetting resin which was diluted by a solvent is impregnated into the damper raw material comprising the cloth material. The solvent is evaporated and the resin tackiness is eliminated. In this state, the damper is thermally molded to obtain a damper main body. The conductive members comprising copper foils or woven wires are adhered onto the upper or back surface of the corrugation.
And the like.
FIG. 3 is a cross sectional view of dies to mold the damper as mentioned above.
The above-mentioned damper raw material or the damper raw material onto which the conductive members were adhered is thermally pressed and molded by upper and lower dies on which a number of convex and concave portions corresponding to the corrugations in FIG. 3 are annularly formed. However, as is well known, upon molding, the material, i.e., the damper raw material is molded while being pulled from the outer peripheral portion to the inner peripheral portion side. Therefore, the shape and number of corrugations, particularly, a width W and a depth D are set to values within ranges such that a damage of the material upon molding and a bending, a deformation, or the like after the molding do not occur.
In the above conventional speaker damper configuration, the conductive members are adhered to the damper main body and the resultant damper is attached. Therefore, there is a drawback such that when the damper is continuously vibrated at a large amplitude for a long time, the conductive members are peeled off from the corrugations and the peeled-off portions are come into contact with the back surfaces of the damper and the cone diaphragm and an abnormal sound is generated. There is also a drawback such that if the abnormal resonance is continued without keeping the proper shape in a state in which the conductive members were peeled off, the conductive members are cut out.
On the other hand, the conventional method of manufacturing the speaker damper described in the above items (1) to (3) has the following drawbacks in terms of the mass productivity.
According to the method of (1) whereby the thermosetting resin is impregnated after the conductive members were attached to the damper raw material, the thermal molding process is executed in a state in which the thermosetting resin is adhered to the conductive members. Therefore, the thermosetting resin adhered to the conductive members is hardened and becomes a good insulative material. When leak wires are connected, the hardened thermosetting resin must be eliminated, and the like. In this manner, the number of manufacturing steps increases. On the other hand, in the case of executing the work such that a masking process is executed to the conductive members or the thermosetting resin adhered to the conductive members is eliminated for the interval when it is hardened, or the like, the number of steps is increased in a manner similar to the above, resulting in an increase in costs.
Further, examination of the material of the adhesive agent which is used, method of coating the adhesive agent, and the like become complicated. For instance, in the case of a general rubber system adhesive agent, it takes a time until a predetermined adhesive strength is obtained. In the case of the adhesive agent of the reactive type such as an acrylic system or the like, a degree of hardness is too high, so that no corrugation can be molded or the like. As mentioned above, a selection range of the adhesive agent is extremely limited.
In the case of the method of (2) whereby after raw material, the solvent is evaporated, and the conductive members are adhered in a state in which the resin tackiness was eliminated, the drawback as in the item (1) which is caused due to the adhesion of the thermosetting resin to the conductive members does not occur. However, with respect to a point that the adhesive agent is used, there are drawbacks such that examination of the material of the adhesive agent and the method of coating the adhesive agent become complicated and the like in a manner similar to the item (1).
In the method of (3) whereby the conductive members are adhered after the damper main body was molded, the drawbacks as in the items (1) and (2) do not exist. However, there are drawbacks such that it is necessary to adhere the conductive members along the corrugations, a method of uniformly coating the adhesive agent along the corrugation is complicated, and the like.
On the other hand, in the case of adhering the conductive members in a state along the corrugations, the conventional speaker damper has the following drawbacks because the width W and depth D of the corrugations are set so as to have the same shape from the inner peripheral portion to the outer peripheral portion.
That is, the copper foils, woven wires, or the like which are generally used as conductive members have drawbacks such that cracks are generated in the conductive members upon molding since the deforming ratio is lower than that of the cloth material such as woven cloth, unwoven cloth, or the like. Particularly, cracks are easily generated near the first concave portion and the first convex portion on the inner peripheral portion side where a force to pull in the material such as conductive members largely acts. This is because the outer peripheral portion sides of the conductive members are cut out and become the free ends and the materials can easily move, but at the inner peripheral portion sides, the inner end is fixed, so that it is extremely difficult to move the material. Accordingly, as the position approaches the inner peripheral portion side, the force to pull in the material is large, so that a more number of cracks are generated in the inner peripheral portion.
As a method of avoiding such a state, there has been known a method whereby the material of the conductive members is divided into two portions at the intermediate position and both of the inner and outer peripheral portion sides are made free or a method whereby the conductive members such as not to generate any crack are arranged. However, the former method has a drawback such that the fairly large number of steps are needed. The latter method has a drawback such that after completion of the molding, internal stresses remain in the conductive members and the conductive members are easily deformed.
Hitherto, a woven wire has been used as conductive wire members. As is well known, the woven wire is formed in a manner such that a copper foil is wound around the twisted fiber and one thin wire-shaped line raw material is formed and a proper number of such line raw materials are selected as necessary and are woven. Therefore, since the copper foil of the woven wire is formed as a continuous spiral shape, the woven wire has a function such that even when the woven thread wire is largely bent, the copper foil can move in conformity with the bent state. Due to this, the wire material is flexible and bending stresses are hardly applied to the copper foil, so that the wire-cut resistance by the metal fatigue is extremely high. Consequently, the woven wire is most frequently used as a conductive material of the speaker which needs the flexibility and vibration resistance.
However, the conventional ordinary woven wire also inevitably has an inconvenience such that cracks are generated due to the vibration of the damper. As shown in FIG. 4, since the copper foils in the adhesive portion of the woven wire attached along the corrugations are fixed to the damper 1, the movable portions of the copper foils can move only on the opposite side of the adhesive portion, that is, only on the upper side in the diagram. Only about half of the inherent capability of the woven wire can be effected. Thus, if the severer conditions are set, the fixed portions of the copper foils, that is, the adhesive portions with the damper cannot help deforming in conformity with the amplitude of the damper, so that there is a fear such that cracks are finally generated due to the metal fatigue and the wire is cut out.